                1. Field of Invention        
This invention relates to hydrofoils, specifically to such devices which are used to create directional movement relative to a fluid medium, and this invention also relates to swimming aids, specifically to such devices which attach to the feet of a swimmer and create propulsion from a kicking motion.
2. Description of Prior Art
None of the prior art fins provide methods for maximizing the storage of energy during use or maximizing the release of such stored energy in a manner that produces significant improvements in efficiency, speed, and performance.
No prior fin designs employ adequate or effective methods for reducing the blade's angle of attack around a transverse axis sufficiently enough to reduce drag and create lift in a significantly consistent manner on both relatively light and relatively hard kicking strokes.
Prior art beliefs, convictions, and design principles teach that highly flexible blades are not effective for producing high swimming speeds. Such prior principles teach that high flexibility wastes energy since it permits kicking energy to be wasted in deforming the blade rather than pushing water backward to propel the swimmer forward. A worldwide industry convention among fin designers, manufactures, retailers and end users is that the more flexible the blade, the less able it is to produce power and high speed. The industry also believes that the stiffer the blade, the less energy is wasted deforming on the blade and the more effective the fin is at producing high speeds. The reason the entire industry believes this to be true is that no effective methods have existed for designing blades and load bearing ribs that exhibit large levels of blade deflection around a transverse axis in a manner that is capable of producing ultra-high swimming speeds. Prior fin design principles also teach that the greater the degree of blade deflection around a transverse axis on each opposing kicking stroke, the greater the degree of lost motion that occurs at the inversion point of each stroke where the blade pivots loosely from the high angle of deflection on one stroke, through the blade's neutral position, and finally to the high angle of deflection on the opposite stroke. Prior principles teach that lost motion wastes kicking energy throughout a significantly wide range of each stroke because kicking energy is expended on reversing the angle of the blade rather that pushing water backward. Also, prior principles teach that the greater the degree of flexibility and range of blade deflection, the greater the degree of lost motion and the larger the portion of each kicking stroke that is wasted on deflecting the blade and the smaller the portion of the stroke that is used for creating propulsion. Furthermore, prior principles teach that such highly deflectable blades are vulnerable to over deflection during hard kicks when high swimming speeds are required. Although it is commonly known that highly deflectable blades create lower strain and are easier to use at slow speeds, such highly deflectable blades are considered to be undesirable and unmarketable since prior versions have proven to not work well when high swimming speeds are required.
Because prior fins are made significantly stiff to reduce lost motion between strokes as well as to reduce excessive blade deflection during hard kicks, prior fins place the blade at excessively high angles of attack during use. This prevents water from flowing smoothly around the low-pressure surface or lee surface of the blade and creates high levels of turbulence. This turbulence creates stall conditions that prevent the blade from generating lift and also create high levels of drag.
Since the blade remains at a high angle of attack that places the blade at a significantly horizontal orientation while the direction of kicking occurs in a vertical direction, most of the swimmer's kicking energy is wasted pushing water upward and downward rather that pushing water backward to create forward propulsion. When prior fins are made flexible enough to bend sufficiently around a transverse axis to reach an orientation capable of pushing water in a significantly backward direction, the lack of bending resistance that enables the blade to deflect this amount also prevents the blade from exerting a significant backward force upon the water and therefore propulsion is poor. This lack of bending resistance also subjects the blade to high levels of lost motion and enables the blade to deflect to an excessively low angle of attack during a hard kick that is incapable of producing significant lift. In addition, prior fin design methods that could permit such high deflections to occur do not permit significant energy to be stored in the fin during use and the fin does not snap back with significant energy during use. Again, a major dilemma occurs with prior fin designs: poor performance occurs when the fin is too flexible and when it is too stiff.
One of the major disadvantages that plague prior fin designs is excessive drag. This causes painful muscle fatigue and cramps within the swimmer's feet, ankles, and legs. In the popular sports of snorkeling and SCUBA diving, this problem severely reduces stamina, potential swimming distances, and the ability to swim against strong currents. Leg cramps often occur suddenly and can become so painful that the swimmer is unable to kick, thereby rendering the swimmer immobile in the water. Even when leg cramps are not occurring, the energy used to combat high levels of drag accelerates air consumption and reduces overall dive time for SCUBA divers. In addition, higher levels of exertion have been shown to increase the risk of attaining decompression sickness for SCUBA divers. Excessive drag also increases the difficulty of kicking the swim fins in a fast manner to quickly accelerate away from a dangerous situation. Attempts to do so, place excessive levels of strain upon the ankles and legs, while only a small increase in speed is accomplished. This level of exertion is difficult to maintain for more than a short distance. For these reasons scuba divers use slow and long kicking stokes while using conventional scuba fins. This slow kicking motion combines with low levels of propulsion to create significantly slow forward progress.
Another problem with many prior fin designs is that they exhibit severe performance problems when they are used for swimming across the surface of the water. While kicking the fins at the water's surface, they break through the surface on the up stroke, and then on the down stroke they “catch” or “slap” on the surface as they re-enter the water at a high angle of and downward movement is abruptly stopped. This instantaneous deceleration creates high levels of strain and discomfort for the user's ankles and lower leg muscles. Because downward movement ceases upon impact with the water, this energy is wasted and is not converted into forward propulsion. Over large distances, this problem can create substantial fatigue for snorkeling skin divers, body surfers, and body board surfers who spend most of their time kicking their fins along the water's surface. It is also a problem for SCUBA divers who swim along the surface to and from a dive site in an attempt to conserve their supply of compressed air. Fatigue and muscle strain to SCUBA divers during surface swims is particularly high because prior SCUBA type fins have significantly long lengthwise dimensions and high angles of attack. This causes increased levels of torque to be applied to the diver's ankles and lower legs as the blade slaps the surface of the water. Because such longer fins create high levels of drag from a decreased aspect ratio, prior SCUBA type fins are significantly slow to re-gaining downward movement after catching on the water's surface. Even below the surface, such prior fins offer poor propulsion and high levels of drag that severely detract from overall diving pleasure.
Prior art fin designs do not employ efficient and methods for enabling the blade to bend around a transverse axis to sufficiently reduced angles of attack that are capable of generating lift while also providing efficient and effective methods for enabling such reduced angles of attack to occur consistently on both light and hard kicking strokes.
Prior art fins often allow the blade to flex or bend around a transverse axis so that the blade's angle of attack is reduced under the exertion of water pressure. Although prior art blades are somewhat flexible, they are usually made relatively stiff so that the blade has sufficient bending resistance to enable the swimmer to push against the water without excessively deflecting the blade. If the blade bends too far, then the kicking energy is wasted on deforming the blade since the force of water applied to the blade is not transferred efficiently back to the swimmers foot to create forward movement. This is a problem if the swimmer requires high speed to escape a dangerous situation, swim against a strong current, or to rescue another swimnmer. If the blade bends too far on a hard kick, the swimmer will have difficulty achieving high speeds. For this reason, prior fins are made sufficiently stiff to not bend to an excessively low angle of attack during hard and strong kicking stokes.
Because prior fin blades are made stiff enough so that they do not bend excessively under the force of water created during a hard kick, they are too stiff to bend to a sufficiently reduced angle of attack during a relatively light stroke used for relaxed cruising speeds. If a swim fin blade is made flexible enough to deflect to a sufficiently reduced angle of attack during a light kick, it will over deflect under the significantly higher force of water pressure during a hard kick. Prior fins have been plagued with this dilemma. As a result, prior fins are either too stiff during slower cruise speeds in order to permit effectiveness at higher speeds, or fins they are flexible and easy to use at slow speeds but lack the ability to hold up under the increased stress of high speeds. This is a major problem since the goal of scuba diving is mainly to swim slowly in order to relax, conserve energy, reduce exertion, and conserve air usage. Because of this, prior fins that are stiff enough to not over deflect during high speeds will create muscle strain, high exertion, discomfort, and increased air consumption during the majority of the time spent at slow speeds.
Because prior art fins attempt to use significantly rigid materials within load bearing ribs and blades to prevent over deflection, the natural resonant frequency of these load bearing members is significantly too high to substantially match the kicking frequency of the swimmer. None of the prior art discloses that such a relationship is desirable, that potential benefits are known, or that a method exists for accomplishing this in an efficient manner that significantly improves performance.
Some prior designs attempt to achieve consistent large scale blade deflections by connecting a transversely pivoting blade to a wire frame that extends in front of the foot pocket and using either a yieldable or non-yieldable chord that connects the leading edge of the blade to the foot pocket to limit the blade angle. This approach requires the use of many parts that increase difficulty and cost of manufacturing. The greater the number of moving parts, the greater the chance for breakage and wear. Many of these designs use metal parts that are vulnerable to corrosion and also add undesirable weight. Variations of this approach are seen in U.S. Pat. No. 3,665,535 (1972) and U.S. Pat. No. 4,934,971 (1988) to Picken, and U.S. Pat. No. 4,657,515 (1978), and U.S. Pat. No. 4,869,696 (1989) to Ciccotelli. U.S. Pat. No. 4,934,971 (1988) to Picken shows a fin which uses a blade that pivots around a transverse axis in order to achieve a decreased angle of attack on each stroke. Because the distance between the pivoting axis and the trailing edge is significantly large, the trailing edge sweeps up and down over a considerable distance between strokes until it switches over to its new position. During this movement, lost motion occurs since little of the swimmer's kicking motion is permitted to assist with propulsion. The greater the reduction in the angle of attack occurring on each stroke, the greater this problem becomes. If the blade is allowed to pivot to a low enough angle of attack to prevent the blade from stalling, high levels of lost motion render the blade highly inefficient. This design was briefly brought to market and received poor response from the market as well as ScubaLab, an independent dive equipment evaluation organization that conducts evaluations for Rodale's Scuba Diving magazine. Evaluators stated that the fin performed poorly on many kick styles and was difficult to use while swimming on the surface. The divers reported that they had to kick harder with these fins to get moving in comparison to other fin designs. The fins created high levels of leg strain and were disliked by evaluators. A major problem with this design approach is that swimmers disliked the snap or click of the blade reaching its limits at the end of each fin stroke.
This design approach produces poor performance for several reasons. The large range of motion of the blade creates lost motion at the inversion point of each stroke where the fins produces little or no propulsion until it reverses its angle of attack and reaches its limit of pivotal movement. The pivotal hinge approach with abrupt limits in motion creates an unsteady and jerky movement and large gaps in the kick cycle where propulsion is missing. The sudden impact of water pressure created as the blade reaches its limits creates a shock to the user's muscles and joints that increases strain, fatigue, and tendency of cramping.
Because the blade hinges near its leading edge and the restraining chord is connected to this leading edge, the moment arm is very short between the hinging axis and the connecting point of the restraining chord. The force of water exerted on the blade between the hinging axis and the trailing edge of the blade is multiplied many times as it is applied to the restraining chord due to the much shorter leading edge moment arm. A heavy kick can produce extremely high stress on the restraining chord. If the chord is elastic, such a high strain can overextend the chord beyond its yielding point so that the blade's angle of attack increases beyond the desired level. The high level of force created by the short moment arm can suddenly extend a relatively small elastic chord (as shown in many of these design approaches) to its inelastic limit to create an abrupt stop in motion that creates a shock to the user's foot and leg. The chord's vulnerability for over extending is increased because of the relatively small cross-section of the restraining chords used in these examples. Repeated use can cause the chord to stretch out over time so that the blade's range of motion further increases over time to inhibit performance. If a larger size chord is used, the blade will not rotate enough under a light kicking stroke. If the chord is small enough to enable the blade to rotate enough during a light kicking stroke, it will abruptly stop at the outer pivotal limit and transfer a sudden shock to the user's leg during a hard kick.
The large distance the chord must stretch during use in order to restrain the blade further inhibits performance. Because the leading edge rotates up and down relative to the foot pocket during use, the chord must stretch vertically over large distances if the blade is to rotate to significantly reduced angles of attack. Because the chord is short at the neutral position, it must stretch and elongate by several times its original length in order to permit the blade to pivot to significantly reduced angles of attack. For this to occur under the low levels of force created during light kicking strokes, the chord must be extraordinarily elastic and have a very low modulus of elasticity (ratio of stress to strain, or load to deflection). The lower the modulus of elasticity, the weaker the material and therefore the less reliable the holding power of the material. Because stronger materials are less elastic, a stronger material capable of holding well under hard kicks will not permit sufficient deflection under light kicks. No effective methods for solving this issue are disclosed.
Because the chord is significantly short at the neutral position in an effort to reduce the occurrence of slack within the chord, the total volume of the chord's material is relatively small. This causes the high stresses in the chord to be distributed over a very small volume of material. This increases vulnerability to over extension and deformation of the material. The small material volume severely limits energy storage within the material. At the inversion point of the kick cycle, the chord provides poor snap back because its energy storage is significantly low and its moment arm is small.
Another problem is that significant levels of slack exist in the chord as the blade pivots close to the neutral position. As the leading edge pivots back toward the neutral position, the alignment of the restraining chord becomes more horizontal and less vertical. This substantially reduces the chord's ability to apply vertical tension to restrain the blade or control its movement. This reduces the ability for energy stored in the elastic chord to be transferred to the blade for effective propulsion. The chord becomes less able to apply propulsive force as it moves the blade from the pivotal limit back to the neutral position. This is highly undesirable and causes energy to be wasted. The lack of vertical tension near the neutral position also permits the blade to move without restraint or control. This increases the severity of the sudden click created as the tension suddenly abruptly increases at the limit of pivotal range. The lack of tension near the neutral position also prevents energy from being stored in this region and the kinetic energy of the blade is wasted. Because the chord has a significant horizontal inclination throughout the entire range of rotation, a significant portion of the tension within the chord is directed in a horizontal direction that does not assist with the vertical restraint or return movement of the blade. This wastes stored energy and destroys efficiency.
If non-elastic chords are used then there is zero snap back energy at the inversion point of each kick and the blade stops with increased shock at the limits of pivoting. Lost motion is extremely high in this situation and performance is exceptionally poor.
Prior fin designs using longitudinal load bearing ribs for controlling blade deflections around a transverse axis do not employ adequate methods for reducing the blade's angle of attack sufficiently enough to reduce drag and create lift in a significantly consistent manner on both relatively light and relatively hard kicking strokes. Many prior art fins use substantially longitudinal load bearing support ribs to control the degree to which the blade is able to bend around a transverse axis. These ribs typically connect the foot pocket to the blade portion and extend along a significant length of the blade. The ribs usually extend vertically above the upper surface of the blade and/or below the lower surface of the blade and taper from the foot pocket toward the trailing edge of the blade. Hooke's Law states that strain, or deflection, is proportional to stress, or load placed on the rib. Therefore the deflection of a flexible rib the load varies in proportion to the load placed on it. A light kick produces a minimal blade deflection, a moderate kick produces a moderate blade deflection, and a hard kick produces a maximum blade deflection. Because of this, prior art design methods for designing load supporting ribs do produce significantly consistent large-scale blade deflections from light to hard kicks.
Prior fin designs using longitudinal load bearing ribs for controlling blade deflections around a transverse axis do not employ adequate methods for reducing the blade's angle of attack sufficiently enough to reduce drag and create lift in a significantly consistent manner on both relatively light and relatively hard kicking strokes.
These ribs are designed to control the blade's degree of bending around a transverse axis during use. Because of the need for the blade to not over deflect during hard kicking strokes, the ribs used in prior fin designs are made relatively rigid. This prevents the blade from deflecting sufficiently during a light kick. This is because the rib acts like a spring that deflects in proportion to the load on it. Higher loads produce larger deflections while lower loads produce smaller deflections. Because prior fins cannot achieve both of these performance criteria simultaneously, prior designs provide stiff ribs to permit hard kicks to be used. The ribs often use relatively rigid thermoplastics such as EVA (ethylene vinyl acetate) and fiber reinforced thermoplastics that have short elongation ranges that are typically less than 5% under high strain and compression ranges that are much smaller. When rubber ribs are used, harder rubbers having large cross sections are used to provide stiff blades that under deflect during hard kicks so that they do not over deflect during hard kicks.
Even if more flexible materials are substituted in the ribs to enable the blade to deflect more under a hard kick, no prior art method discloses how to efficiently prevent the blade from over deflecting on a hard kick.
The vertical height of prior stiffening ribs often have increased taper near the trailing edge of the blade to permit the tip of the blade to deflect more during use. Flexibility is achieved by reducing the vertical height of the rib since this lowers the strain on the material and therefore reduces bending resistance. Again, no method is used to provide consistent deflections across widely varying loads. The approach of reducing the vertical height of a rib to increase flexibility is not efficient since it causes this portion of the rib to be more susceptible to over deflection and also reduces performance by minimizing energy storage within the rib. U.S. Pat. No. 4,895,537 (1990) to Ciccotelli reduces the height of a narrow portion on each of two longitudinal support beams to focus flexing in this region. This makes the ribs more susceptible to over deflection and minimizes energy storage.
Another problem is that prior fin design methods teach that in order to create a high powered snap-back effect the ribs must attain efficient spring characteristics by using materials that have good flexibility and memory but have relatively low ranges of elongation. Elongation is considered to be a source of energy loss while less extensible thermoplastics such as EVA and hi-tech composites containing materials such as graphite and fiberglass are considered to be state of the art for creating snap back qualities. These materials do not provide proper performance because they provide substantially linear spring deflection characteristics that cause the blade to either under deflect on a light kick or over deflect on a hard kick. Furthermore, these materials require that a small vertical thickness be used in order for significant bending to occur during use. This greatly reduces energy storage and reduces the power of the desired snap back.
The highly vertical and narrow cross-sectional shape of prior ribs makes them highly unstable and vulnerable to twisting during use. When the vertical rib is deflected downward, tension is created on the upper portion of the rib as well as compression on the lower portion of the rib. Because the material on the compression side must go somewhere, the lower portion of the rib tends to bow outward and buckle. This phenomenon can be quickly observed by holding a piece of paper on edge as a vertical beam and applying a downward bending force to either end of the paper. Even if the paper is used to carry a force over a small span, it will buckle sideways and collapse. This is because the rib's resistance to bending is greater than its resistance to sideways buckling. If more resilient materials are used in prior art rails, then the rails will buckle sideways and collapse. This causes the blade to over deflect.
Some prior art ribs have cross-sectional shapes that are less vulnerable to collapsing, however, none of these prior art examples teach how to create similar large-scale blade deflections on both light and hard kicking strokes.
U.S. Pat. No. 5,746,631 to McCarthy shows load bearing ribs that have a rounded cross-section, no methods are disclosed that permit such rails to store increased levels of energy or experience substantially consistent blade deflections on both light and hard kicking strokes. Although it is stated that alternate embodiments may permit the lengthwise rails to pivot around a lengthwise axis where the rails join the foot pocket so that the rails can flex near the foot pocket, no method is identified for creating consistent deflections on light and hard kicks. It is mentioned that the blades can be pivotally attached to the foot pocket to permit pivoting around a transverse axis and that once the blades have pivoted to their desired range limit, a suitable stopping device can be use to halt all other movement either gradually or immediately, and that such a stopping device may also provide some spring-like tension to snap the blades back to a neutral orientation at the end of a stroke. No specific and efficient type of stopping device, spring system, or efficient method of pivotally attaching the blades to the foot pocket is stated. It is mentioned that a small zone of decreased thickness may be created near the foot pocket to permit the base of the stiffening members, or side rails, to achieve some degree of backward bending around a transverse axis near the foot pocket. No mention is given as to which dimension such a reduction in thickness occurs. Also, the rails are stated as being significantly rigid and this prevents a reduction in the thickness of the rails from permitting the blade to bend to a substantially large reduced angle of attack around a transverse axis on a light kick while preventing the blade from over deflecting or collapsing during a hard kick. The preference for having spring tension to return the blade to a neutral blade position does not include methods for increasing energy storage and return during use.
U.S. Pat. No. 4,689,029 (1987) to Ciccotelli shows two flexible longitudinal ribs extending from the foot pocket to a blade spaced from the foot pocket. Although Ciccotelli states that these ribs have elliptical cross-sections to prevent twisting, he also states that these flexible ribs are made sufficiently rigid enough to no over deflect on hard kicks. The patent states that the “flexible beams are made of flexible plastic and graphite or glass fibers may be added to increase the stiffness and strength. The flexible beams have to be stiff enough to prevent excessive deflection of the blade on a hard kick by the swimmer otherwise a loss of thrust will result.” This shows that he believes that stiffer ribs are required to provide maximum speed. This also shows that Ciccotelli believes that the use of softer and highly extensible materials in the ribs will cause over deflection to occur during hard kicks and therefore unsuitable for use when high swimming speeds are needed. FIG. 2 shows that the range of deflection (17) is quite small and does not produce a sufficiently large enough reduction in the angle of attack to create proper lift and to prevent stall conditions. This shows that Ciccotelli is not aware of the value of larger blade deflections. This limited range of deflection shows that the flexible beams he uses are only slightly flexible and relatively rigid. In addition to providing insufficient deflection, no method is given for creating such deflections in a consistent manner on both light and hard kicks. Ciccotelli also states that the elliptical cross-section of the beams near the foot pocket is approximately 1.500 by 0.640, and that a larger cross section would be required for stiffer models. The cross-sectional measurements are at a height to width ratio of approximately 3 to 1. If this ratio were used with soft and highly extensible materials, the ribs would buckle sideways and collapse during use. Also, the top view in FIG. 1 shows that the ribs bend around a slight corner before connecting to the wire frame. This corner creates high levels of instability within the rib and makes the rib even more vulnerable to buckling, especially when more extensible materials are used. No adequate methods or structure are disclosed that describe how to avoid buckling on softer materials or how to obtain consistent large-scale deflections on both light and hard kicks. No methods are disclosed for storing large sums of energy within the ribs and then releasing such energy during use.
U.S. Pat. No. 4,773,885 (1988) to Ciccotelli is a continuation-in-part of U.S. Pat. No. 4,689,029 (Ser. No. 842,282) to Ciccotelli that is described above. U.S. Pat. No. 4,689,029 displays that Ciccotelli still does not disclose a method for creating large scale blade deflections on light kicks while simultaneously preventing over deflection on hard kicks. Although U.S. Pat. No. 4,773,885 describes flexible beams that are made of a rubber-like thermoplastic elastomer, the purpose of these flexible beams are to enable to beams to flex sufficiently enough to enable a diver to walk across land or through heavy surf. No method is disclosed to for designing such beams to create consistent large-scale blade deflections on varying loads. No mention is made of any attempts to create large-scale blade deflections on light kicks. The only benefit listed to having flexible beams is to enable the diver to walk across land while carrying equipment. No mention is made of methods for creating and controlling specific blade deflections and no mention is made for optimizing the storage of energy. This shows that Ciccotelli is not aware that such benefits are possible and is not aware of any methods or processes for creating and optimizing such benefits. Furthermore, Ciccotelli states in column 3 lines 20 through 37 that “The beams 2 are sufficiently flexible to bend enough so that the wearer, with his foot in the pocket 1 can walk along a beach in a normal fashion, with his heel raising as his foot rolls forward on its ball. Nevertheless, beams 2 are sufficiently stiff that during swimming, the flexible beams 2 flex only enough to provide good finning action of the blade 4, in accordance with the principles described in the above-referenced application Ser. No. 842,282.” He states that the beams must be stiff in accordance with the principles of Ser. No. 842,282 (U.S. Pat. No. 4,689,029) which only shows a substantially small range of blade deflection (17) in FIG. 2 of the drawings. U.S. Pat. No. 4,773,885 shows no desired range of blade deflection in the drawings and specifically states that during swimming the beams act in accordance with what is now U.S. Pat. No. 4,689,029 which shows in FIG. 2 the small range of flexibility Ciccotelli believes is ideal. This range is too small since it does not permit the blade to reach a sufficiently reduced angle of attack to efficiently create lift and reduce stall conditions. Because he states that the beams should be stiff enough to not over deflect during a hard kick and only shows a small range of deflection (17) in FIG. 2, it is evident that Ciccotelli believes that deflections in excess of range 17 in FIG. 2 is an “excessive deflection” that will cause a “loss of thrust”. He discloses no other information to specify what he believes to be an excessive angle of deflection. This shows that shows that Ciccotelli does not intend his flexible beams to be used in a manner that enables the blade to experience significantly high levels of deflection. This also shows that Ciccotelli is unaware of any benefits of large-scale blade deflections and is unaware of methods for designing ribs in a manner that create new benefits or new unexpected results from large-scale blade deflections.
Another problem with U.S. Pat. No. 4,773,885 is that the cross sectional shape of the rail creates vulnerability to twisting and buckling. Ciccotelli admits that the beams tend to buckle and twist when the blade deflects while walking on land. If the beams buckle and twist under the larger deflections occurring while walking, the beams will also buckle and twist if the beams are made with sufficiently flexible enough grades of elastomeric materials to exhibit high levels of blade deflections during use. The reason the rails are vulnerable to buckling is that the first stages of twisting causes the rectangular cross-section to turn to a tilted diamond shape relative to the direction of bending. The upper and lower corners of this portion of the beam are off center from the beam axis (the axis passing through the cross-sectional geometric center of the beam) of the beam during bending. These corners also extend higher above and below the beam axis relative to bending than the upper and lower surfaces of the rectangular cross section that existed before twisting. Because stresses are greatest at the highest points above and below the beam's neutral surface (a horizontal plane within the beam relative to vertical bending, in which zero bending stress exists), these tilted corners have the highest levels of strain in the form of tension and compression. Because these corners and the high strain within them are oriented off center from the beam axis, a twisting moment is formed which cause the beams to buckle prematurely while bending. As the beam twists along its length, bending resistance and twisting moments vary along the length of the beam. This causes the beams to bend unevenly and forces energy to be lost in twisting the beam rather than creating propulsion. Although Ciccotelli provides extra width at the lower end of the beam to reduce the bulking there under compression, he states that this is done to reduce buckling if the blade jams into the ground while walking. He does not state that he this is done to create any benefits while swimming. He does not use cross sectional thickness to create new and unobvious benefits while swimming. Because desires small ranges of blade deflection, he does not disclose a method for using cross-sectional shape in a manner that enables high levels of deflection to occur on light kicks while preventing excessive deflection on hard kicks. He also does not disclose any methods for using cross-sectional shapes to provide increased energy storage.
None of the prior art discloses methods for designing longitudinal load bearing ribs that are able to permit the blade to reach high levels of provide specific minimum and maximum reduced angles of attack around a transverse axis that are desired at slow swimming speeds and maximum reduced angles of attack that are desired at high swimming speeds along with an efficient and effective method for achieving these minimum and maximum angles regardless of swimming speeds.
U.S. Pat. No. 2,950,487 to Woods (1954) uses a horizontal blade mounted on the upper surface of the foot which rotates around a transverse axis to achieve a reduced angle of attack on both the upstroke and the down stroke. This design suffers from high levels of lost motion and creates a shock to the users foot and leg as the blade reaches its limits on each kick. No adequate method is used to store energy during use.
U.S. Pat. No. 3,084,355 to Ciccotelli (1963) uses several narrow hydrofoils that rotate along a transverse axis and are mounted parallel to each other in a direction that is perpendicular to the direction of swimming. The blades rotate loosely in a manner that creates lost motion and no method is used to efficiently store and release energy.
U.S. Pat. No. 3,411,165 to Murdoch (1966) displays a fin which uses a narrow stiffening member that is located along each side of the blade, and a third stiffening member that is located along the central axis of the blade. Although oval shaped ribs are shown, the use of metal rods within the core of these ribs prevents bending from occurring. No method is disclosed for optimizing the storage and recovery of energy. A major problem with scoop designs is that the angle of attack is high and significant backpressure develops within each pocket causing water to spill around the side edges of the pocket like an overfilled cup. Induced drag is high, propulsion is poor and only a small amount of water is discharged aftward.
French patent 1,501,208 to Barnoin (1967) employs two side by side blades that are oriented within a horizontal plane and extend from the toe of the foot compartment. Each of the blades have a triangular wedge shaped transverse cross-section with the thicker portion existing along the outer edge and the thinner portion on the inside edge. The cross-sectional or end view shown displays that no load bearing ribs are used. No methods are disclosed for creating consistent large-scale deflections under varying loads or for creating increased energy storage.
German patent 259,353 to Braunkohlen (1987) suffers from many of the same problems and structural inadequacies as Barnoin's fin discussed above Each of the blades have a triangular wedge shaped transverse cross-section with the thicker portion existing along the outer edge and the thinner portion on the inside edge. The cross-sectional or end view shown displays that no load bearing ribs are used. No methods are disclosed for creating consistent large-scale deflections under varying loads or for creating increased energy storage.
U.S. Pat. No. 4,007,506 to Rasmussen (1977) uses a series of rib-like stiffeners arranged in a lengthwise manner along the blade of a swim fin. The ribs are intended to cause the blade to deform around a transverse axis so that the trailing portions of the blade curl concavely in the direction of the kicking stroke. The blade employs no method for adequately decreasing induced drag. The blade's high angle of attack stalls the blade and prevents smooth flow from occurring along its low-pressure surface. No methods are disclosed for creating consistent large-scale deflections under varying loads or for creating increased energy storage.
U.S. Pat. No. 4,025,977 to Cronin (1977) shows a fin in which the blade is aligned with the swimmers lower leg. This design is highly inefficient on the upstroke and creates high levels of lost motion. No methods are disclosed for creating for reducing lost motion or for creating increased energy storage.
U.S. Pat. No. 4,541,810 to Wenzel (1985) employs load supporting ribs that have a cross-section that is wide in its transverse dimension and thin in its vertical dimension. The rib is intended to twist during use. The thin vertical height of the rib prevents efficient energy storage and no methods are disclosed for creating consistent large-scale blade deflections with the ribs.
U.S. Pat. No. 4,738,645 to Garofalo (1988) employs a single blade that deforms under water pressure to form a concave channel for directing water toward the trailing edge. The load bearing ribs are made of rigid material that place the blade at excessively high angles of attack. The rib's cross section has a thin horizontal dimension and a tall vertical dimension that make the blade vulnerable to twisting and buckling during use. No methods are disclosed for creating consistent large-scale deflections under varying loads or for creating increased energy storage.
U.S. Pat. No. 4,781,637 to Caires (1988) shows a single fin designed to be used by both feet in a dolphin style kicking motion. It uses a transversely aligned hydrofoil that extends from both sides of a centrally located foot pocket and rotates around a transverse stiffening rod. The central portion of the blade is fixed to a metal plate to prevent variation in the angle of attack there while the outer tip portions are described as being free to rotate throughout an arc of approximately 90 degrees. This creates a twist along the transverse length of the blade that creates stress forces of tension and compression that can prevent the tips from twisting to a substantially reduced angle of attack. In order for the tips to twist, the blade material must succumb to these stress forces of tension and compression that extend diagonally across the transverse length of each half of the blade. Because this forms a complex stress field over a large volume of material within the large transverse dimension of the blade, the blade material exhibits high levels of bending resistance and tends to buckle to avoid succumbing to these forces. The portion of the blade that tends to buckle exists between the trailing edge and an imaginary line drawn from the trailing portion of the central stiffening plate to the outer tips of the transverse stiffening rod. Such buckling enables the tip regions of the blade to deflect to an excessively low angle of attack during use that is incapable of producing lift. If the blade material is rigid enough to avoid buckling during use it will not deflect sufficiently enough at the tips to efficiently create lift and the majority of the blade stalls and creates drag. If the material is flexible enough to avoid the transversely diagonal stress forces, the blade buckles under strain and the buckled portion of the blade pivots loosely and lost motion is created. If material is chosen that is flexible enough to bend gradually during use to reach the desired 90-degree pivot range stated during a hard kick, the blade will under deflect during a light kick. If the blade is loose enough to deflect to the desired 90 degree angle during a light kick, it will over deflect during a hard kick. This design creates lost motion and no methods are disclosed for creating consistent large-scale deflections under varying loads or for creating increased energy storage.
U.S. Pat. No. 4,857,024 to Evans (1989) shows a fin that has a relatively thin flexible blade and uses no load bearing ribs. The center portion of the blade is made thicker to create increased bending resistance along the center. The drawings show that during use the stiffer central portion of the blade arches back around a transverse axis to an excessively reduced angle of attack where the blade then slashes back at the end of the stroke in a snapping motion to propel the swimmer forward. The blade deflects to an excessively low angle of attack to efficiently generate lift. The thin blade offers poor energy storage and snap back energy is low. Underwater tests conducted by ScubaLab, an independent dive equipment evaluation organization, utilized men and women divers wearing full scuba gear that swam numerous test runs over a measured 300-foot open ocean course. These tests found that this design consistently produced the lowest top end speeds of any production fins tested. No methods are disclosed for creating consistent large-scale deflections under varying loads or for creating increased energy storage.
Although the specification and drawings mention the formation of a snap back motion, no S-shaped substantially longitudinal sinusoidal waves are displayed in the drawings or described in the specification. Although the blade has a thicker central portion, this thicker portion is significantly too thin to permit the use of substantially soft materials that have significantly high elongation and compression rates since such flexibility would cause the blade to deflect excessively. As a result, this design is forced to use stiffer materials having significantly lower elongation and compression ranges under the loads created during kicking strokes. These types of materials support a natural resonant frequency that is significantly higher than the kicking frequency of a swimmer's strokes. No mention is made to suggest that such a condition is anticipated or desired. Although the tip regions are designed to flex relative to the thicker blade portion along the fin's center axis, the drawings and specification do not disclose a method for simultaneously creating opposing oscillation phases in an S-shaped manner along the length of the blade in general or along the length of the more flexible side regions of the blade.
The open toe foot pocket that encloses only the upper portion of the foot and permits the lower portion of the foot to pivot freely and independently of the blade, prevents efficient longitudinal wave generation along the blade because the forward portion of the foot near the toes is unable to exert a pivotal motion on the blade as opposing leverage is applied by the foot between the upper portion of the foot near the heel and the lower portion of the foot near the toes. This prevents the swimmer from applying leverage from the forward portions of the foot to effectively create a pivoting motion to the blade with rotations of the ankle. Because Evans' foot pocket is described as permitting free rotation of the lower portion of the foot relative to the blade in an effort to reduce ankle strain, it is evident that Evans is not aware of a method for effectively reducing ankle strain while significantly minimizing or eliminating movement of the lower portion of the foot relative to the blade.
U.S. Pat. No. 2,423,571 to Wilen (1944) shows a fin that has a stiffening member along the central axis of the blade that has a thin and highly flexible membrane extending to either side of the central stiffening member. The thin and flexible membrane is shown to undulate during use and have opposing oscillation phases along the length of the blade's side edges, in which a sinusoidal wave has adjacent peaks and troughs displayed by convex up and convex down ripples. The central stiffening member, or load bearing member does not have opposing oscillation phases and therefore Wilen does not anticipate the need for this to occur or provide an effective manner for permitting this to occur in a manner that prevents the member from over deflecting during a hard kicking stroke. Although it is mentioned that a more flexible material may be used at the blade of the central stiffening member to provide limited movement and pivoting near the foot pocket, no effective method is disclosed for permitting this more flexible material to allow significantly large scale blade deflections to occur during a light kick while preventing over deflection during a hard kick.
The thin membrane used in this fin is far too thin to effectively propagate a lengthwise wave having opposing phases of oscillation since the dampening effect of the surrounding water quickly dissipates the small amount of wave energy stored in this thin material. Instead of creating propulsion, the thin blade will flop loosely without having enough bending resistance to accelerate water. Rather than moving water, the thin membrane will over deflect and stay substantially motionless while the foot and stiffening member move up and down. Even though it is mentioned that stiffening members can be used to reinforce the side portions of the blade no method is disclosed for effectively preventing these portions from over deflecting during hard kicking strokes while also permitting large scale blade deflections to occur during light kicking strokes. No methods are disclosed that permit significantly increased energy to be stored and then released in the blade. Because such methods are not used or disclosed, this fin does not produce significant propulsion and is not usable.
From both the top view and the side view of FIG. 15 and FIG. 16, it can be seen that Wilen's fin creating a longitudinal wave that has many peaks and troughs across the length of the blade. This means that the frequency of the propagated wave is significantly higher than the frequency of kicking strokes. Wilen does not disclose methods for correlating blade undulation frequency, wavelength, amplitude, and period with the swimming stroke that creates new levels of performance and unexpected results.
A book reference found in the United States Patent and Trademark Office in class 115/subclass 28 labeled “3302 of 1880” shows a horizontally aligned reciprocating propulsion blade. The blades flex backward around a transverse axis in response to water pressure. No methods are disclosed for creating consistent large-scale deflections under varying loads or for creating increased energy storage.
U.S. Pat. No. 3,453,981 to Gause (1969) uses a series of horizontally aligned propulsion blades that are intended to convert wave energy into forward motion on a boat. No methods are disclosed for creating consistent large-scale deflections under varying loads or for creating increased energy storage.